The Performance of the Benesi-Hildebrand Method in Measuring the Binding Constants of the Cyclodextrin Complexation

Abstract

prompted us to examine in detail the sources and magnitude of its inaccuracies in measuring binding constants, especially those of cyclodextrin (CD) complexation. Such a study will surely benefit the future research, though surprisingly it has not been conducted before. Experimental The basic approach of the present study was computer simulation. The computer program, written in Borland C++ 5.0, was run on a PII400 computer. CD complexation was investigated as a typical system, for CD was one of the most frequently encountered host molecules in the field of molecular recognition. In the simulation, the real concentration of the substrate was chosen as 1.00× 10 ‐4 M for all the solutions. The real binding constant (K) was chosen as 50, 1000 or 10000 M ‐1 . The molar absorption constant of the free substrate ( e0) was taken as 5000 m 2 /mol, while the molar absorption constant of the bound substrate (e∞ ) was chosen as 4950, 4850, or 4750 m 2 /mol, respectively. Seven different real CD concentrations were used: 0.0000, 0.0025, 0.0040, 0.0055, 0.0070, 0.0085 and 0.010 M. Herein, the absorption of CD was presumably zero. Three replicate solutions were prepared at every CD concentration, and their absorption values were averaged to offer the absorption value at the given CD concentration. It was noteworthy that the present selections of host and guest concentrations for simulation were reasonable, for they were based on the practice in real experiments.